Detectability of gravitational waves from binary black holes: Impact of precession and higher modes

TL;DR

Current gravitational wave search templates for binary black holes often omit precession and higher modes, which can significantly reduce detection sensitivity for certain high-mass, high-mass-ratio systems, especially at advanced detector sensitivities.

Contribution

This study quantifies the impact of neglecting precession and higher modes on detection volume loss for binary black holes with high mass ratios and masses, highlighting the need for improved templates.

Findings

Loss of up to 25% in sensitive volume for certain systems.

Neglecting precession and higher modes affects detection efficiency.

Impact is more severe at advanced detector sensitivities.

Abstract

Gravitational wave templates used in current searches for binary black holes omit the effects of precession of the orbital plane and higher order modes. While this omission seems not to impact the detection of sources having mass ratios and spins similar to those of GW150914, even for total masses $M > 200M_{\odot}$; we show that it can cause large fractional losses of sensitive volume for binaries with mass ratio $q \geq 4$ and $M>100M_{\odot}$, measured the detector frame. For the highest precessing cases, this is true even when the source is face-on to the detector. Quantitatively, we show that the aforementioned omission can lead to fractional losses of sensitive volume of $\sim15\%$, reaching $>25\%$ for the worst cases studied. Loss estimates are obtained by evaluating the effectualness of the SEOBNRv2-ROM double spin model, currently used in binary black hole searches, towards gravitational wave signals from precessing binaries computed by means of numerical relativity. We conclude that, for sources with $q \geq 4$, a reliable search for binary black holes heavier than $M>100M_\odot$ needs to consider the effects of higher order modes and precession. The latter seems specially necessary when Advanced LIGO reaches its design sensitivity.